A singulation system for singulation or dicing electronic components, such as semiconductor substrates or packaged semiconductor devices, comprises at least a spindle system and a carrier support such as a chuck table. The axis of the spindle system is orthogonal to the axis of the chuck table and a theta axis table is located on top of the chuck table. The spindle system typically includes either one or two high speed rotary shafts with a cutting blade comprising a circular saw blade each.
Dicing may be performed on the semiconductor substrate in one direction by moving the chuck table under a spindle axis while the saw blade is cutting the semiconductor substrate on a carrier, such as a saw jig, on the theta axis table of the chuck table. The spindle axis may index line by line to complete all the cutting lines required in one direction. Next, the theta table on the chuck table rotates 90 degrees about the theta axis to perform dicing in a direction orthogonal to the first direction. Thus, the semiconductor substrate is singulated into rectangular units.
As singulation is operated by rotating the circular saw blade at high speed, for safety reasons, it is important to monitor and detect the condition of the blade in order to halt the singulation process when the blade is chipped or otherwise damaged. Additionally, the blade will wear out after a period of sawing, resulting in the blade having a reduced diameter. The wearing-out rate of the blade should be monitored regularly in order to accurately adjust the cutting depth of the blade to maintain a constant sawing depth and to replace the blade at an appropriate time.
FIG. 1 is a schematic drawing of a typical through beam sensor 100 located near a saw blade 102 for detecting blade damage. The sensor 100 is placed at a fixed distance from the edge of the blade 102 such that a sensing line 106 monitors the edge of the blade 102 continuously and is able to detect a chipped blade. However, the position of the sensor 100 relative to the edge of the blade must be adjusted manually with a screw 104 when the diameter of the blade 102 decreases as the blade wears off. During adjustment of the sensor 100, the singulation operation must be stopped, which affects productivity. It would be beneficial to be able to monitor damage to the saw blade without interrupting the singulation operation to manually adjust the position of the sensor 100.
Conventionally, optical or contact methods may be used for detecting and measuring the extent of wearing off of a saw blade. These methods are illustrated in FIG. 2. The optical method uses an optical sensor 106 located at a fixed position at some distance from a rotary blade 102. The sensor 106 comprises a light emitting component and a light receiving component positioned opposite each other across a gap which receives the saw blade. Separate water and air nozzles 108 are located within the gap for cleaning the light emitting and receiving components of the optical sensor 106.
After the water nozzles are deactivated, water droplets remaining on the light emitting and receiving components are removed by air jets directed from the air nozzles. Therefore, the light emitting and receiving components are kept clean and dry, that is, they are free from contaminants such as chips and sawing dust from the singulation process. This allows accurate measurement of the extent of wear of the rotary blade. Measurement of wear is conducted by indexing the rotary blade 102 downwards to an optical sensing line in the gap and its index position at the sensor 106 is recorded. When the blade diameter is reduced due to wearing off during singulation, the blade 102 would have to be indexed further downwards to be level with the same optical sensing line. The difference in the index positions is equivalent to the extent of wear of the blade.
In the contact method, the blade 102 is indexed downwards to a standard reference surface 110 located at some distance from the blade 102. When the blade 102 touches the reference surface 110, the index position is recorded. Next, if the blade diameter is reduced as the blade 102 is worn off, the blade 102 will be required to index further to become level with the reference surface 110. The difference in index positions is equivalent to the extent of wear of the blade 102.
Both the contact and optical methods of measuring the extent of wear of the saw blade as described above are slow and inhibit normal machine operation as the saw blade 102 during the singulation operation is far from the optical sensor or the reference surface. It would thus be advantageous to be able to measure an extent of wear of the blade without moving the saw blade 102 over relatively large distances for detecting its edge.
A prior art example of an optical method for damage and wear detection of a saw blade is found in U.S. Pat. No. 6,552,811 entitled “Cutting Blade Detection Mechanism for a Cutting Machine”. It discloses a dicing machine comprising a typical through beam sensor similar to that illustrated in FIG. 1 herein for detecting a chipped saw blade. It further discloses an optical sensor comprising light emitting and receiving components as described above for measuring wear value of the saw blade. Contamination of the sensor by the chips and sawing dust during singulation is cleansed by jetting water followed by jetting air at the sensor. Whilst this increases the reliability of readings with regard to the blade, multiple nozzles comprising separate water supply nozzles and air supply nozzles are deployed. This makes the machine complex and increases the number of components required. It is desirable to reduce the number of components for easier machine maintenance and to reduce the need for stocking additional spare parts.
Another prior art example of a singulation system which uses the optical method for detecting the extent of wear is Japanese Patent Publication No. 2006-287111 entitled “Cutting Device and Blade Condition Detecting Method”. This prior art discloses a single blade detection sensor for both damage detection and wear detection of a saw blade. The sensor can be indexed by migration means to two different locations for separately carrying out the functions of damage detection and wear detection of the saw blade. Switching means is employed to toggle the sensor between the two locations for carrying out the two detection functions. The toggling between the two detection functions at the two locations is undesirable as this affects the reliability and stability of measuring the blade wear value. Additional time is also required to repeatedly move the sensor between the two locations to perform the two functions. It would be advantageous to eliminate the need for switching between the two detection modes and locations to simplify the measuring algorithm and to achieve increased accuracy and stability.